Rotary locking device



1959 J. w. JARRETT ETAL 2,917,942

ROTARY LOCKING DEVICE Filed Jan. 31, 1958 INVENT JOHN w. .1422 :vmsrr a.RICE ATWRMEYJ United States Patent ROTARY LOCKING DEVICE John W.Jarrett, Fortville, and Everett L. Rice, Indianapolis, Ind., assignorsto the United States of America as represented by the Secretary of theNavy Application January '31, 1958, Serial No. 712,594

'3 Claims. (Cl. 74-504) (Granted under Title 35, US. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

The present invention relates to a locking device and more particularlyto a locking device that can be applied to an electrical component suchas a rotary switch, potentiometer, or the like, to prevent accidentalrotation thereof.

Control panels, such as those used in aircraft, often have large numbersof electrical components such as switches and potentiometers, andbecause of space limitation these components are often mounted closelytogether. Consequently, it is very likely that a component may beunintentionally rotated when it should not be, thus creating an insafecondition. The locking device disclosed herein actually serves a dualpurpose in that it locks a rotary device against accidental rotation andalso has a detent arrangement for setting a rotary device in adesiredposition.

The locking device disclosed herein is adaptable for mounting to manyheretofore available components and requires only a very minormodification of the component to be operable thereon. A shaft is axiallyslidably attached to the existing shaft of an electrical component, andthe attached shaft has at least one lug that is engageable with aplurality of slots in a shaft bushing. The attached shaft is resilientlybiased outwardly to retain the lugs within one of the slots and, when inthis position, the attached shaft is locked from rotation. When it isdesired to rotate the attached shaft, it is first necessary to move itinwardly until the lug is disengaged from the slot. The shaft is thenfree to be rotated.

It is therefore a general object of the present invention to provide adevice that will prevent accidental shaft rotation of an electriealdevice,

Another objeet of the invention disclosed herein is to provide a devicefor locking the shaft of an electrical component in a plurality ofpositions.

Qther objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing wherein;

Figure 1 is a plan view showing the shaft end of an embodiment of thepresent invention;

Figure 2 is a partial sectional View taken on line 2-2 of Fig e Figure 3is a partial sectional view taken on line 3-3 of Figure 1 and showingthe attached shaft moved inwardly;

Figure 4 is a plan view showing a shaft and bushing arrangement; and

Figure 5 is a plan view similar to the view shown in Figure 4 butshowing the shaft rotated.

Referring now to the drawing, there is shown in Figures 1-3, a lockingdevice 11 that is attached to an elec- 2,917,942 Patented Dec. 22, 1959trical component 12, such as a rotary switch or potentiometer. Theelectrical component 12 is of the type adaptable for panel mounting andhas a threaded por= tion 13 through which extends a rotatable shaft 14.

The threaded portion 13 of component 12 is passed through a bore 15 inthe end of a cylindrical housing 16 and a nut 17 is provided to hold thehousing in position. A washer 18 having a lug 19 thereon is positionedaround the threaded portion 13, and the lug 19 engages a hole 21 in theend of the cylindrical housing 16 to prevent rotation of the housingrelative to the component 12.

A bushing 22 is attached to the end portion of housing 16 by means ofscrews 23, and a shaft 24 is rotatably mounted within the bore ofbushing 22. The shaft 24 has a large diameter portion and a smalldiameter portion, the small diameter portion having a flat 25 thereonfor facilitating the fastening of a knob (not shown). The large diameterportion of shaft 24 is slightly smaller than the bore of bushing 22 andthe shaft is axially slidable within the bushing and also capable ofrotation. As shown in Figure 4 of the drawing, shaft 24 has a pluralityof lugs 26 radiating from the large diameter portion thereof, and theselugs are engageable with a plurality of slots 27 in the inner end ofbushing 22. Although three lugs 26 and three slots 27 are shown forpurposes of illustration, it should be understood that either a lesseror greater number could be used equally well.

Shaft 24 has a bore 28 and a slot 29 in the large diameter portion thatpermits the coupling of shaft 24 to the shaft 14 of component 12. A pin31 is press-fitted into shaft 14 and slot 29 is slidably engageable withpin 31. As shown in Figure 2 of the drawing, slot 29 has sufficientdepth to allow shaft 24 to move axially inwardly until lug 26 on shaft24 is cleared from slot 27, at which time the shaft 24 is unlocked andfree to be rotated.

As shown in Figures 2 and 3 of the drawing, a coil spring 32 is providedwithin the cylindrical housing 16 between the inner face of the housingand the inner face of shaft 24 to bias the shaft 24 outwardly. Thus whenlugs 26 are engaged in slots 27, spring 32 retains the shaft 24 in astationary position and therefore the shaft 24 is maintained in a lockedposition,

In operation, the shaft 24 is normally maintained in a locked positiondue to the lugs 26 being engaged in slots 27. When it is desired torotate the shaft 14 of component 12, it is first necessary to move shaft24 inwardly until the lugs 26 are cleared from slots 27. Figure 3 of thedrawing shows this condition, with the spring 32 being compressed andthe lug 26 moved inwardly to clear slot 27. While still applying aninward pressure, the shaft 24 is then rotated in a desired direction anda rotating force is transferred from shaft 24 to pin 31 in shaft 14, todrive shaft 14, which is the component shaft. As shown in Figure 5 ofthe drawing, after lugs 26 are rotated from being in alignment withslots 27, it is no longer necessary to apply inward pressure on shaft24, and shaft 24 can be rotated until the lugs are forced into the nextadjacent slots by the spring 32.

It can thus be seen that the device herein diselosed provides aconvenient locking arrangement for a component shaft in that it is firstnecessary to apply an in, wardly directed force and then, while applyingthis force, apply a rotating force. Thus aecidental rotation of a shaftis not likely to occur,

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that the in- 3 vention may be practiced otherwise than asspecifically described.

What is claimed is:

'1. A locking devicefor an electrical component comprising, acylindrical housing member having an open end and an inside face andremovably attached to the shaft end of an electrical component having arotatable shaft, a bushing fixedly attached to said housing member andhaving a plurality of radial slots, and attached shaft having an insideface and mounted for rotary movement and axially slidable movement insaid bushing with SZliL. side face on said shaft being opposite saidinside face on said cylindrical housing, saidattached shaft having alarge diameter portion having :a diametral slot on the end thereof andhaving means for engaging said plurality of slots in said bushing, meanson said rotatable shaft of said component in slidable engaging relationwith said diametral slot in said attached shaft, and means positionedwithin said housing member for biasing said attached shaft in adirection outwardly from said electrical component.

2. A locking device as set forth in claim 1 wherein said means forbiasing said attached shaft comprises a compression spring mountedbetween the inside face of said housing member and the inside face ofsaid attached shaft.

3. A locking device for an electrical component comprising, acylindrical housing member having an open end and an inside face andremovably attached to the shaft end of an electrical component having arotatable shaft, a bushing fixedly attached to said housing member andhaving a plurality of radial slots, an attached shaft having an insideface and mounted for rotary movement and axially slidable movement insaid bushing with said inside face on said shaft being opposite saidinside face on said cylindrical housing, said attached shaft having alarge diameter portion having a diametral slot on the end thereof and atleast one lug extending perpendicular to the longitudinal axis of saidattached shaft for engaging said radial slots, a pin fixedly attached tosaid rotatable shaft of said component and in slidable engagement withsaid diametrar slot in said attached shaft, and a compression springmounted between the inside face of said housing member and the insideface of said attached shaft for biasing said attached shaft in adirection outwardly from said electrical component.

References Cited in the file of this patent UNITED STATES PATENTS1,274,471 Todd Aug. 6, 1918 2,438,045 Gerhardt et al Mar. 16, 19482,561,482 Schostak July 24, 1951 2,631,203 Mekelburg Nov. 10, 19532,651,281 Nathan Sept. 8, 1953 2,704,466 Way Mar. 22, 1955 2,849,891Mills Sept. 2, 1958 FOREIGN PATENTS 797,938 France Feb. 24, 1936

